Whenever an image is made of something (anything), it is always presented from a particular unique perspective. Furthermore, the image will most likely have no inherently useable scale and, depending on the resolving power of whatever device is used to make the image, details in the image may be minimal. On this point, it is noted that the more pixels there are in an image, the higher will be the resolution and fidelity of the image. Issues arise, however, when an image (i.e. a photo) is to be used to identify the location of an object (target) in the image. In particular, issues of perspective, scale and resolution can be troublesome when the image has been created by a relatively low-fidelity camera (i.e. a photo image), and is taken from an unspecified location (e.g. from an aerial vehicle). Moreover, as suggested above, these issues may become crucial when the intended use of the image is for locating something in the image (e.g. a geo-location task).
In order for a photo image to be useful for geo-location purposes, the photo first needs to be somehow registered. In this case, registration is necessary so the perspective of the image can be defined and a metric scale for use with the image can be established. This can be done in any of several different ways. For example, the Log-Polar Transformation (LPT) is a well known technique that correlates selected features from different images (i.e. a “test” image and a “reference” image). Specifically, this is done to register the test image with the reference image (see A. D. Ventura and A. Rampini, “Image registration by recognition of corresponding structures,” IEEE Trans. on Geoscience and Remote Sensing, May 1990, pp. 305-314). With LPT, as with other techniques, however, the resolution level of the image (i.e. number of pixels in the image) can become a significant issue when near real time registration of the image is required. An important reason for this is that the more pixels there are in an image (i.e. the higher the fidelity of the image) the larger will be the computational load, and the longer will be the processing time. This will be so, even for relatively low-fidelity, low-resolution images.
In light of the above, it is an object of the present invention to provide a system and method for registering a low-fidelity test image with a high-fidelity reference image, in near real time, wherein the computational load and processing time for registration is minimized. Another object of the present invention is to provide a system and method for registering a test image with a reference image wherein pixels from different images are respectively decimated and correspondingly correlated for subsequent selection and further evaluation in an image registration process. Still another object of the present invention is to provide a system and method for registering a low-fidelity test image with a high-fidelity reference image that is relatively simple to manufacture, is easy to use and is comparatively cost effective.